Gas filter unit

ABSTRACT

The invention concerns a gas filter unit or cartridge type, including a filter material put together to form one or several filter bags, and a support frame of essentially U-shaped cross-sectional configuration, including a web portion and two lateral leg members in adjoining relationship, the filter material closest to the mouths of the filter bags being clamped in position between said lateral leg members. In accordance with the invention, the frame includes profile sections of a flexible material, preferably a plastics material, at least one of said lateral leg members being hingedly interconnected with the web portion, in addition to which locking means are provided to retain the corresponding lateral leg member in its clamping position in which it is pivoted into engagement with the other lateral leg member.

GAS FILTER UNIT

The subject invention relates to a gas filter unit of cartridge type,comprising a filter material put together to form one or several filterbags, and a support frame of essentially U-shaped cross-sectionalconfiguration including a web portion and two adjoining lateral legmembers in adjoining relationship therewith, the filter material closestto the mouths of the filter bags being clamped in position between saidlateral leg members.

Gas filter units of the type outlined above are known for instance fromU.S. Pat. No. 4,056,373. The frame designed to support the filter bagsat the mouths thereof usually is either a metal frame having a U-shapedcross-sectional configuration, the lateral leg members or lateralflanges of which are clamped about the material closest to the filterbag mouths, or preferably a frame of a plastics material to which thefilter bag and portions are secured by welding by means of athermoplastic or otherwise hardenable material. This type of securementcould also be used in a metal frame. Since the requirements of productrecyclability are becoming stricter it is necessary that the varioustypes of material incorporated in a product be easily separated to besubsequently subjected to destruction or recycling in a manner adaptedto each individual material. In the case of filter units of the kindoutlined above it has hitherto been impossible, or at least entailedconsiderable difficulties, to separate the support frame from the veryfilter bag material. In addition, complex equipment is required toinsert and secure the filter bag material to the support frame in themanufacture of the filter cartridge.

The main purpose of the invention is to provide a gas filter unit whichmay be manufactured in a simple and cost-saving manner and which mayalso be easily separated into its various structural materials inconnection with destruction and/or recycling.

This purpose is achieved in accordance with the invention by means of agas filter unit which is essentially characterized in that the framecomprises profile sections of a flexible material, preferably of aplastics material, at least one of said lateral leg members beinghingedly interconnected with the web portion, and in that locking meansare provided to retain the corresponding lateral leg member in itsclamping position wherein it is pivoted into engagement with the otherlateral leg member. Owing to this arrangement the filter bags are easilyinserted into the frame part and the frame part may be clamped theretosimply by the lateral leg members being folded inwards, the frame partbeing efficiently secured to the filter bags following activation of thelocking means. By releasing the locking means the frame may be detachedfrom the filter bags in a simple manner and both components bedestructed and/or recycled separately.

Preferably, the pivotable lateral leg members and the web portion areintegrally interconnected as a unit via a thinner hinge portion. Theassembly is thus greatly facilitated because the entire cross-section ofthe frame pieces consist of captively interconnected pieces.

Preferably, those edge portions of the lateral leg members that faceaway from the web portion are bent inwards so as to form afilter-material securing nip when in their clamping position. Owing tothis bent configuration resilient clamping portions are formed thatefficiently retain the filter material, independently of any changes ofthe shape of the material that may be caused for instance by changes inthe environment in which the gas filter unit is used.

Preferably, the locking means are in the shape of hook means formed onrespectively the web portion and the lateral leg members and spaced adistance from the respective hinge connection between the web portionand the lateral leg members, said hook means interengaging in thefilter-material clamping position. Owing to this arrangement a simplelocking device is produced, which owing to its position in relation tothe hinge allows the lateral leg members to be efficiently maintained intheir clamping position.

Preferably the support frame consists of straight lateral frame piecesand of corner pieces fitted thereto an extending across the framecorners. This allows the various pieces to be manufactured in a simplemanner, particularly when the frame side pieces are extruded profilesections.

Preferably, the web portion of the frame side pieces is configured as ahollow section while at the same time the corner pieces have a coreformed with insertion tenons fitting the cavity of the hollow section.In this manner interconnection of the various components making up theframe is facilitated.

Preferably, the corner pieces are formed with flap-like lateral legmembers formed integrally with and hingedly interconnected with theassociated corner piece core on either side of the corner angle, whichleg members, like the lateral leg members of the frame side pieces, arearranged to be pivoted inwards to assume a clamping position in whichthey are retained by interacting hook means formed respectively on thelateral leg members and on the corner piece body corresponding to theweb portion of the frame side pieces. Owing to this arrangement itbecomes easy to insert the edge portions of the filter bags in theassembled frame along the entire circumference thereof and toefficiently clamp the filter bag material in position along the entireframe. Preferably, one lateral leg member of at least the frame sidepieces is formed with a back-up shoulder on which rest filter bagsupport bars extending between facing frame side pieces. The provisionof such a back-up shoulder allows loose support bars to be positioned soas to bridge the space between oppositely positioned frame side pieces,thus efficiently supporting the filter material when the latter isassembled so as to form several filter bags the mouths of which aredistributed across the surface of the support frame.

Preferably, the web portions, the lateral leg members, the hook means,the clamping means as well as the support bar back-up shoulders of theframe side pieces all are parts of the cross-sectional configuration ofan extruded profile section and thus they extend over the entire lengthof the corresponding frame side piece. This arrangement results inhighly simplified manufacture because all parts included in the frameside piece construction may receive their final configuration already inthe very extruding process.

Further advantages of and characteristic features of the invention willappear from the dependent claims.

One embodiment of the invention will be described in closer detail withreference to the accompanying drawings, wherein

FIG. 1 is a partly cut perspective view of a ventilation duct or thelike in which is mounted a gas filter unit in accordance with theinvention,

FIG. 2 illustrates in a cut part view a frame side piece included in thegas filter unit in accordance with the invention as well as the filterpart associated therewith in a sequence during the assembly of saidparts,

FIG. 3 illustrates a profile section which, when mounted, forms theframe side pieces of the gas filter unit,

FIG. 4 illustrates the frame of FIG. 2 in the mounted position,

FIG. 5 is a perspective view showing the corner pieces of the frame inthe unfolded position.

FIG. 6 is a corresponding perspective view as seen from the oppositeside of the corner piece in FIG. 5,

FIG. 7 illustrates the corner piece in a perspective view when in itsclamping position, however, for the sake of clarity separated from theassociated frame side piece and any filter bag material,

FIG. 8 is a cross-sectional view of a frame side piece in the clampingposition thereof, and

FIGS. 8a-8c illustrate on enlarged scale the various details formingpart of the frame cross-section.

FIG. 1 illustrates a gas filter unit in accordance with the invention,said unit comprising a support frame 1 and a number of filter bags 2that are connected to the support frame. In accordance with theembodiment illustrated the filter bags are made from a pleated filtermaterial. Each individual filter bag is formed with an opening 3 whichis positioned in the area of the support frame 1 and which is delimited,in addition to by the support frame, by folds 4 made in the filtermaterial intermediate the bags. It is of course equally possible for thesupport frame 1 to support one filter bag only the opening of which isthen delimited entirely by the support frame. In this case the folds 4naturally are superfluous.

The gas filter unit 1, 2 forms a cartridge which may be inserted intoand removed from a ventilation duct 5 or the like. In accordance withthe embodiment illustrated the filter unit 1, 2 is housed in a filtercabinet 6 forming part of the ventilation duct 5. Preferably, the filtercabinet is connected to the rest of the ventilation duct by means ofinterconnection flanges 7 formed at the cabinet ends. Numeral reference8 designates guide rails extending transversally across the filtercabinet by means of which rails the support frame 1 may be inserted fromone end of the filter cupboard. To make the gas filter unit accessibleand to allow replacement thereof the filter cupboard is provided with anopenable side hatch 9. Via this hatch it thus is easy to remove thefilter unit and to insert a new one in its place in the ventilationduct.

The support frame 1 has an essentially U-shaped cross-sectionalconfiguration and the filter bag material 2 at the mouth ledge of thefilter bags is inserted in the frame opening side, where it is clampedin position in the manner to be described in closer detail below. Thesupport frame consists of corner pieces 10 bridging the frame cornerangles and of frame side pieces 11 interconnecting the corner pieces. Asmost clearly apparent from FIG. 8 the frame side pieces have anessentially U-shaped cross-sectional configuration including a webportion 12 and adjoining side leg members 13 and 14, respectively. Asmost clearly apparent from FIG. 7, the corner pieces consist of a core15, which corresponds to the web portion of the frame side pieces, andof two lateral leg members 16 and 17, respectively, interconnected withthe core. In accordance with the embodiment illustrated the frame sidepieces preferably are extruded profile sections configured such that theweb portion 12 is interconnected with each lateral leg member 13, 14 viathinner hinge-forming areas 18 and 19, respectively. The support frame,i.e. its side pieces 11 as well as its corner pieces 10 preferably aremade from a destructable or recyclable material, preferably a plasticsmaterial. The web portion 12 forms a hollow section having, asillustrated in the drawing figures, a rectangular internal circumference20. Thus, the lateral leg members 13, 14 may be pivoted about the hingesformed by the folding indications 18, 19, from the flat unfoldedposition illustrated in FIG. 3 to a position, in which snap ribs 21 and22, respectively, having a hook shaped cross-sectional configuration andpositioned at distance a, b, respectively, from the hinges, inter-engagewith correspondingly shaped snap ribs 23 and 24 on the web portion 12and thus assume the position illustrated in FIG. 8. The lateral legmembers are formed at their free end edges with an arcuately inwardlycurved portion 25 and 26, respectively, extending the lateral legmembers in such a manner that in the folded position they essentiallymeet while forming a nip for retaining material positioned therebetween,such as the edge portions of the filter bags as will be described morein detail below. In order to achieve satisfactory holding force the edgeportions 25, 26 are provided with barb-like teeth 25a, 26a, as mostclearly apparent from FIG. 8c. As appears from this drawing figure theteeth 25a, 26a in the two clamping portions 25, 26 are alternatelydisplaced. Owing to the arrow-like or barb-like configuration of thecross-section of the snap ribs 21-24 serving as gripping rails they arecomparatively easy to move into juxtaposed relationship because theyslide against each other's oblique faces until they snap together asillustrated in FIG. 8. Because of the barb like interconnection they arehowever, more difficult to pull apart. However, the gripping portionsare constructed in such a manner that the gripping force may beabolished, possibly with the aid of suitable tools, to allow the frameto be loosened from the filter bags to be destructed or recycled whenthe filter unit no longer is efficient.

Similarly, the corner pieces comprise a central web portion or core 27which is formed integrally with lateral leg members 30, 31 via hingeconnections 28, 29. Like the frame side pieces the web portions 27 areformed with gripping portions 35 and 36, respectively, cooperating withgripping portions 37 and 38, respectively on the lateral leg members inthe folded-together position illustrated in FIG. 7. In addition, thelateral leg members are formed with inwardly curved edge portions 32,33, the latter preferably also being provided with gripping knurlscorresponding to the gripping means formed on the lateral leg members ofthe frame side pieces. The lateral leg members of the corner pieces formwing-like means projecting from the core 27 and formed with an obliqueedge adjacent the corner 34 and with a straight-cut edge at the oppositeend. 27a designates tenons projecting past the lateral leg members andthe external shape of these tenons essentially corresponds to the innerprofile 20 of the frame side piece web portion 12. When pivoted inwardsinto juxtaposed position the edge portions 32 and 33 form a nip, asillustrated in FIG. 7, designed to securely hold in position materialintroduced between said edge portions, as will be described in closerdetail in the following. The lateral leg members on either side of thecorner 34 are symmetrically shaped and have a cross-sectionalconfiguration corresponding to the cross-sectional configuration of theframe side pieces, thus forming a continuous extension of the frame sidepieces through the support frame corners. Preferably, theinterconnection tenons 27a are formed with snap beads or the like,cooperating with corresponding elements formed in the frame side piecesin order to retain the corner pieces securely attached to the framepieces in the assembled condition of the support frame. In addition, thelateral leg members 30 of the corner pieces as well as the lateral legmembers 13 of the frame side pieces are provided with flanges 39 and 40,respectively, intended to form a receiving surface to support carrierbeams 41, the latter extending, in the mounted condition of the gasfilter unit, between oppositely positioned frame side pieces for thepurpose of supporting the filter bags 2 in the folds thereof indicatedin FIG. 1 by means of reference 4.

Preferably, the frame side pieces are extruded in the comparatively flatshape indicated in FIG. 3 from a suitable plastics material. In thisprocess, the areas indicated by a and b, respectively, in the lateralleg portions may be gripped by means of a suitable pulling means toextract the profile section through the extruder die. Owing to thecomparatively symmetrically shape of the profile section the resultingexpelling force will be smooth and even in relation to the extruder die.The frame side pieces are then severed to suitable lengths and areinterconnected by means of the corner pieces. In FIG. 2 the lateral legportion 13 is shown folded towards web portion 12 in which position thecorresponding gripping ribs are interlocked. The filter material 2,which in accordance with the embodiment illustrated consists of a numberof filter bags which are sewn together or welded together, is placed inthe frame by applying the bag mouth edge on top of the gripping edge 25of the corresponding side leg member 13. The support bars 41 which inaccordance with the embodiment illustrated has a T-shapedcross-sectional configuration, are placed in position with their endportions in contact with the support flange 40 and they support thefilter bag material in the area between the discrete filter bag parts.After folding the lateral leg member 14 downwards in the directionindicated by arrows 42, the marginal portion of the filter material ismaintained in position, clamped in the nip formed by the lateral legmember clamping portions 25, 26, as most clearly indicated in FIG. 8 andand FIG. 8c. In the same manner, the filter material is maintained inposition by the side leg members 30, 31 of the corner pieces.

The invention is not limited to the embodiment described and illustratedin the drawing figures merely as an example but could be varied as toits details within the scope of the appended claims without departingfrom the fundamental idea of the invention. Thus, it is within the scopeof the invention to configure the frame side pieces as well as thecorner pieces in such a manner that one of the lateral leg members isfixed. In this case, the frame may be given the cross-sectional shapeillustrated in FIG. 2 according to which the web portion 12 wouldhowever be formed integrally with the lateral leg member 13, i.e.,without any coupling means. The corresponding modification could beapplied to the corner pieces, in which case for instance the lateral legmember 30 would be fixedly interconnected with the core or web portion27 in the position illustrated in FIG. 7. Although, in accordance withthe embodiment shown the coupling parts consist of snap ribs extendingalong the entire longitudinal extension of the profile sections it iswithin the scope of the invention to provide the frame side pieces, andalso the corner pieces, with separate coupling means at selected pointsalong their length. The invention is not either limited to the cavityconfiguration of web portion 14 illustrated. Its cross-sectionalconfiguration could also deviate from the rectangular shape. It islikewise possible to modify the configuration of the web portion suchthat the locking means are supported spaced from their associated hinge18, 19 with the aid of other means than the closed hollow section. Insuch cases guide flanges or other suitable means preferably are arrangedto guide the corner pieces coupling tenons 27a.

Owing to the curved configuration of the edge portions 25, 26 of thelateral leg portions 13, 14 and of the corresponding portions of thecorner pieces an efficient resiliency is obtained which attributes tothe secure fixation of the filter material in position, independently ofdimensional changes of the material in the frame, which changes may becaused for instance by the environmental effects to which the frame isexposed during service. When the filter unit is no longer usable it isremoved and replaced by a new one. The old filter unit is dismantled,i.e. the lateral leg members 14 and 31, respectively, are pried open,whereupon the filter bags are loosened from the frame and from thesupport bars 41. The support bars and the filter frame could then eitherbe re-used in a fresh filter unit or be destructed or re-melted to beagain extruded into the desired configuration.

It is likewise within the scope of the invention to co-extrude theprofile sections in different materials. For instance, the web portioncould be extruded from a rigid material possessing good stability,together with lateral leg portions of a material possessing highresiliency and possibly also exhibiting a comparatively high degree ofsoftness in the area of the gripping portions.

We claim:
 1. A gas filter unit comprising:a filter material constructedto form at least one filter bag having a mouth; a support frameincluding a web portion and two lateral leg members in adjoiningrelationship therewith, said lateral leg members each having a free endedge and a fixed end edge, each of said free end edges having a clampingportion, whereas each respective clamping portion is bent so as to facethe other, each clamping portion delimited by complementary teeth, atleast one of said lateral leg members being hingedly interconnected withthe web portion at said fixed end edge, each of said lateral leg membersincluding a respective locking means for locking each of said lateralleg members in a clamping position against said web portion, whereinsaid at least one leg member is adapted to pivot into engagement withthe other lateral leg member so as to lock said at least one leg memberto said web portion and to lock said filter material between said teeth.2. The gas filter unit as claimed in claim 1, wherein the at least onepivotable lateral leg member and the web portion are integrallyinterconnected at a hinge zone of a reduced thickness.
 3. The gas filterunit according to claim 1, wherein the teeth of the clamping portionsform a filter material securing nip when in the clamping position. 4.The gas filter unit as claimed in claim 1, wherein said locking means iscomprised of at least one set of complementary and interlocking hooks,one of said hooks formed on the web portion and the other of said hooksformed on said at least one lateral leg, each of said hooksinterengaging in the clamping position.
 5. The gas filter unit asclaimed in claim 1, wherein the support frame is comprised of straightframe side pieces and of corner pieces wherein the web portion isconfigured as a hollow section defining a cavity, and the corner piecesinclude a core with insertion tenons fitting into the cavity of thehollow section.
 6. A gas filter unit as claimed in claim 5, wherein theframe side pieces are extruded profile sections.
 7. The gas filter unitas claimed in claim 5, wherein the corner pieces are formed withflap-like lateral leg members formed integrally with and hingedlyinterconnected with the associated corner piece core on either side ofthe corner angle, which leg members, like the lateral leg members of theframe side pieces, are arranged to be pivoted inwards to assume aclamping position in which position they are retained by interactinghook means formed respectively on the lateral leg members and on thecorner piece body (27) corresponding to the web portion of the frameside pieces.
 8. The gas filter unit as claimed in claim 7, wherein thebody and the lateral leg members of the corner pieces are configured inconformity with the cross-sectional configurations of the web portionand of the lateral leg members of the frame side pieces, respectively.9. The gas filter unit as claimed in claim 5, wherein one lateral legmember of at least the frame side pieces is formed with a back-upshoulder on which rest filter bag support bars extending between facingframe side pieces.
 10. The gas filter unit as claimed in claim 1,wherein the web portions, the lateral leg members, the hook means, theclamping means as well as the support bar back-up shoulders of the frameside pieces all are parts of the cross-sectional configuration of anextruded profile section and thus extend over the entire length of thecorresponding frame side piece.
 11. The gas filter element as claimed inclaim 1, wherein the locking means are formed with engagement portionsinteracting through snap action.
 12. The gas filter element as claimedin claim 11, wherein the engagement portions are designed with a hookshape adapted to ensure that the resistance of said engagement portionagainst pivotment of the lateral leg members of the clamping position isconsiderably weaker than the resistance in the opposite direction.